Install a pressure switch with the little bleed off needle valve on the side. Install an in-tank check valve between the pump and tank. Plumb a 1/4" copper tube from the check valve 1/8" NPT bleed off port to the unloader needle valve. Adjust to desired cut-out pressure.
Some Curtis setups use the exhaust valve as the check valve, so an unloading pressure switch won"t work until you do the check valve install. Remove all the flyweights and levers, you won"t need them anymore.